Flow field characteristics and energy loss model of the effective upstream flow region of orifice in liquid jet

Abstract

Orifice jets commonly adhere to the thick-walled orifice jet mechanism or the thin-walled one, where the difference between the two orifice jet mechanisms is generally considered to be caused after the fluid enters the orifice. However, ignoring the energy loss before entering the orifice could be inaccurate and even misleading. Therefore, we studied the flow behavior in the upstream flow region of thick-walled orifices (small orifices) and thin-walled ones (large ones). Firstly, the concept of the effective upstream flow region of orifice was proposed based on the film theory. It can be simplified into an approximate hemispherical multi-channel parallel contractive flow field. Then, the experiments of the effective upstream flow region were conducted by the streamlined contractive orifices with equivalent energy loss. The proportion of the energy loss before the fluid enters the orifice to the total energy loss was obtained. In addition, the maximum impact range of the effective upstream flow region was remarked by theoretical derivation, and local resistance coefficient functions were established based on the CFD simulation results. Finally, a semi-theoretical model of energy loss in this region was developed. It can quantitatively measure the proportion of increased energy consumption caused by the sucked air inside orifice, well verifying the eddy energy consumption, which provides a scientific exclusion method for predicting the complex form resistance.